The present disclosure relates to managing entries of a translation look-aside buffer (TLB). In particular, the present invention relates to avoiding a complete TLB purge when modifying states of entries in a TLB, maintaining valid the TLB entries.
Real storage manager (RSM) routines administer the use of real storage and direct the movement of virtual pages between auxiliary storage and real storage. The RSM routines make all addressable virtual storage appear as real or physical storage to a user, while only the virtual pages necessary for execution are kept in real storage.
The RSM assigns real storage frames on request, associating virtual storage addresses with real storage addresses. To maintain the assignments, the RSM maintains data structures such as Region Tables, Segment Tables, and Page Tables for dynamic address translation (DAT). A translation look-aside buffer (TLB) contains virtual address-to-real address translations that may be accessed for quick lookups when a virtual address is referenced. When a referenced virtual address is not located in the TLB, the real address must be obtained by building a new virtual-to-real address translation.
When DAT information is changed, or when information related to virtual or real addresses is changed, TLB entries corresponding to the DAT information, as well as TLBs containing the TLB entries, are purged, such as with a Compare and Swap and Purge (CSP) instruction which updates the tables of the RSM and purges the TLB of each central processing unit (CPU) of a system. Purging the TLB results in longer processing times to obtain virtual-to-real address translations, since RSM will now have to build the virtual-to-real translations no longer residing in the TLB.